Types of Parkinson’s Disease

Parkinson's disease (PD) is classified by type based on its cause and age of onset. Idiopathic PD (Parkinson's disease) occurs in persons around 60. Early-onset PD occurs in younger patients, often before the age of 50.

There are also secondary parkinsonism and atypical parkinsonism. These conditions have similar PD symptoms but are caused by something else, like a drug, stroke, or a primary neurodegenerative disease.

This article will review the different types of Parkinson's disease, including the causes of secondary parkinsonism and atypical parkinsonism.

Idiopathic Parkinson's Disease

Idiopathic (the cause is unknown) Parkinson's disease is the most common type of PD. It affects older individuals, with an average age of onset around 60.

The symptoms of idiopathic PD are divided into two categories—motor (movement) and non-motor.

Motor symptoms of PD include:

• Shaking (tremor)
• Slowness of movement (bradykinesia)
• Rigidity (stiffness)
• Poor balance

Motor symptoms tend to start out mild and worsen slowly over time. They also begin on one side of the body and eventually spread to the other side.

Non-motor symptoms of PD can develop before a diagnosis of PD is even suspected.

Non-motor symptoms include:

• Mood disorders like depression, anxiety, and loss of motivation (apathy)
• Sleep disorders
• Fatigue
• Loss of sense of smell
• Urinary urgency
• Reduced cognitive function, such as forgetfulness
• Psychosis with hallucinations (seeing or hearing things that aren't there)

Early-Onset Parkinson's

Early-onset PD, also known as youth-onset PD, is a rare type of PD that affects individuals between the age of 21 and 40 or 50 years (studies use varying age cut-offs).

Symptoms of early-onset PD are similar to idiopathic PD, but they tend to progress more slowly. Regardless, since people are in the prime of their life when diagnosed, symptoms tend to have a more drastic psychological and social impact.

A distinguishing feature of early-onset PD is that side effects related to levodopa (a drug used to treat the condition) like dyskinesia (uncontrollable body movements) and the wearing-off phenomenon (in which the drug becomes less effective) tend to occur earlier compared to idiopathic PD.

In order to try to delay these undesirable side effects, doctors initially treat patients with early-onset PD with dopamine agonists or monoamine oxidase inhibitors. These are alternative drugs to levodopa.

Familial Parkinson's

Most cases of PD are sporadic, meaning they are not inherited and are caused by a complex interplay of genetic and environmental factors.

That said, around 10 to 15% of cases of PD are believed to be inherited. These familial cases of PD are caused by mutations (DNA changes) in certain genes that are passed down from genetic parent to child.

Scientists have discovered several genes linked to PD and uncovered how mutations within these genes influence risk and disease development. As an example, mutations in the gene SNCA are linked to autosomal dominant Parkinson's disease.

Secondary Parkinsonism

With secondary parkinsonism, a person may develop one or more of the same movement-related symptoms as those seen in Parkinson's disease.

Unlike Parkinson's disease, secondary parkinsonism occurs as a result of an underlying process or factor, such as a drug, head trauma, toxins, brain infection, or stroke. All of these causes block or interfere with dopamine levels or function in the brain.

Drug-Induced Parkinsonism

Drug-induced parkinsonism (DIP) is the most common type of secondary parkinsonism. It occurs when symptoms of PD develop after taking a medication, most commonly an antipsychotic drug.

The motor symptoms of drug-induced parkinsonism mimic those in idiopathic PD, except they tend to occur equally on both sides of the body.

Doctors can confirm a diagnosis of DIP by stopping the drug potentially causing it. Once the drug is stopped, symptoms should resolve within two months.

Vascular Parkinsonism

Vascular parkinsonism, also called arteriosclerotic parkinsonism, is a form of secondary parkinsonism in which motor symptoms seen in PD develop from small vessel (lacunar) strokes in the substantia nigra or the basal ganglia (two areas of the brain).

A stroke occurs when a blood vessel that supplies the brain is blocked or bleeds into the brain. Without adequate blood flow, brain cells die, and various symptoms manifest depending on the area of the brain affected.

The diagnosis of a stroke can be confirmed with a magnetic resonance imaging (MRI) test of the brain. Smoking cessation and controlling risk factors like high cholesterol or high blood pressure (hypertension) can help prevent strokes.

Atypical Parkinsonism

"Atypical parkinsonism" is an umbrella term for neurodegenerative diseases that share similar symptoms of PD, including:

• Dementia with Lewy bodies
• Multiple system atrophy
• Progressive supranuclear palsy
• Corticobasal syndrome

These four diseases are all characterized by abnormal protein buildup in brain cells. The type and location of the protein deposition vary among the different diseases.

Distinguishing PD from these parkinsonian diseases can be challenging, particularly in the early stages of the disease.

Dementia with Lewy Bodies

Dementia with Lewy bodies (DLB) typically occurs in individuals over the age of 50 and is characterized by the presence of significant and fluctuating thinking, memory, and attention difficulties (dementia).

Detailed and recurrent visual hallucinations and rapid eye movement (REM) sleep behavior disorder (acting out vivid, mostly unpleasant dreams by calling out or moving your arms and legs) are additional core symptoms.

Both DLB and PD are characterized by the presence of Lewy bodies in the brain. Lewy bodies are abnormal clumps of a protein called alpha-synuclein.

Other possible symptoms of DLB include:

• Delusions (false beliefs)
• Depression, anxiety, and apathy
• Repeated falls
• Behavior changes like agitation and aggression

Patients with DLB also commonly experience parkinsonism (symptoms such as tremors, slowness, and stiffness), although they are not essential for diagnosis.

Multiple System Atrophy (MSA)

Multiple system atrophy (MSA) is a rare neurodegenerative disease that results from the loss of nerve cells involved in regulating movement and the autonomic nervous system.

As with LBD and idiopathic PD, MSA is characterized by the presence of clumps of alpha-synuclein protein. Unlike in PD, the clumps of alpha-synuclein protein in MSA are found in support cells (called glial cells) and not nerve cells.

Symptoms of MSA tend to develop in a person's 50s and progress rapidly over a period of five to 10 years.

MSA symptoms are highly variable and may include:

• Motor symptoms like slow movements, stiffness, and walking/balance problems
• Lightheadedness, dizziness, and fainting
• Involuntary loss of urine (urinary incontinence)
  
• REM sleep behavior disorder
• Slurred speech or quavering voice
• Difficulty swallowing (dysphagia)
• Abnormal eye movements
  

Progressive Supranuclear Palsy (PSP)

Progressive supranuclear palsy (PSP), also known as Steele-Richardson-Olszewski syndrome, is an uncommon parkinsonian syndrome.

Its onset, like idiopathic PD, is in late middle age; however, the symptoms of PSP worsen more rapidly than PD.

PSP is a form of tauopathy—a neurodegenerative disease characterized by abnormal deposits of the protein tau in the brain. Alzheimer's disease is also a tauopathy.

The symptoms of PSP are highly variable but commonly include problems with walking and balance resulting in falls, as well as difficulty controlling eye movements.

Other symptoms of PSA may include:

• Cognitive and behavioral problems, such as forgetfulness, apathy, and impulsivity
• Difficulty swallowing (dysphagia)
• Slowed movements and neck/upper trunk rigidity
• Sleep disturbances, especially insomnia (impairment of ability to fall asleep or stay asleep)
• Drooling and excessive saliva production

Corticobasal Syndrome

Corticobasal syndrome (CBS) is a rare neurodegenerative disease that develops at an average age of 64 and causes changes in movement. Language and cognitive problems may also occur.

Like PSP and Alzheimer's disease, in CBS, abnormal levels of the protein tau collect in brain cells, eventually leading to the death of those cells.

Most commonly, the motor symptoms of CBS affect one side of the body, such as stiffness of one arm, leg, or both.

Other motor symptoms of CBS include:

• Apraxia (being unable to perform a movement on command, despite their desire to)
• Dystonia (involuntary muscle contractions)
• Myoclonus (quick, muscle jerks that are out of your control)
• Alien limb phenomenon (involuntary movement of a limb while simultaneously feeling like the limb is foreign, or not part of your body)

Conditions Associated With Parkinson’s

Some neurological conditions mimic and/or are related to or linked to Parkinson's disease.

Essential Tremor

Essential tremor (ET) causes rhythmic shaking of both hands and arms. It may also involve the head, trunk, voice, and rarely, the legs. ET often runs in families and is a disorder that slowly worsens over time.

For most cases of tremor, distinguishing ET from PD is relatively straightforward. The tremor of ET is an action tremor, meaning it's brought on by movement, like eating or tying shoelaces, or when the arms are outstretched. The tremor of PD, on the other hand, occurs at rest.

That said, patients with PD often have an action tremor prior to developing more obvious PD signs. Experts aren't sure if this action tremor is ET or an early sign of PD.

Normal Pressure Hydrocephalus

Normal pressure hydrocephalus (NPH) is a neurological disease of older adults that develops when cerebrospinal fluid (CSF) builds up in the brain's ventricles, or cavities.

The classic symptoms of NPH are:

• Difficulty walking
• Dementia
• Urinary incontinence

Parkinsonian motor symptoms, with the exception of resting tremor, also frequently occur among people living with NPH. This can make differentiating between the two diseases tricky.

A careful examination of symptom characteristics and timeline can be helpful. Motor symptoms in PD are asymmetric early on in the disease (typically symmetric in NPH), and dementia in PD does not occur until the later stages.

Summary

Parkinson's disease (PD) is a neurodegenerative disease that affects dopamine-producing nerve cells in the brain. There are three main types of PD—idiopathic, early-onset, and familial. There are also conditions that share similar symptoms and signs of PD but are caused by something else, such as a drug, stroke, or other neurological process.

A Word From Verywell

If you think you or your loved one may be experiencing symptoms of PD like stiff muscles, shaking, or slower walking, please reach out to your primary care physician or a movement disorder specialist.

While these symptoms may be from PD, they could also be attributed to another condition. A thorough evaluation will help you obtain the right diagnosis so you can move forward with a proper treatment plan.